This invention relates to a modulation/demodulation system or apparatus, for example, a modulation/demodulation system or apparatus for outputting infrared rays modulated by transmission data modulated with FSK (frequency shift keying) or by the base-band transmission data, and an information processing system or apparatus.
In data communication between an information processing system, such as a personal computer, and a peripheral equipment, such as a printer, there is a system employing a modulation/demodulation system (modem), besides a system of directly coupling the equipment by a cable.
Among the modems, there is a modem which effects a close range data communication using light communication, such as infrared rays, referred to hereinafter as infrared or IR modem, besides a modem employing cable connection between the equipment. The modems employing the infrared rays are employed nowadays extensively because there is no necessity of connecting the IR modems with a cable, and the equipment can be installed or moved easily.
Meanwhile, due to increase in memory IC capacity, high IC integration and high density packaging, personal computers are reduced in size, such that portable personal computers or pocketable personal computers, or so-called electronic memoranda, are used extensively. Since these personal computers are small-sized, the above-mentioned IR modems are effective for data communication. Some versions of the personal computers are provided with built-in IR modems.
The present Assignee has proposed a portable information processing system having light data transmitting function in our co-pending JP Patent Application No. 2-298983 corresponding to U.S. patent application Ser. No. 07/787,037, now U.S. Pat. No. 5,210,927. The system includes two portable information processing units, each having on its upper surface a transmission section having light emitting devices and a receiving section having light receiving devices for effecting light data transmission, these units having their upper surfaces abutted against each other to effect data transmission and reception.
Among commonplace well-known apparatus for effecting data transmission using IR light, there are remote control commanding units, or commanders, for operating TV receivers or video tape recorders by a remote control operation.
Meanwhile, there is a demand for remote controlling electronic equipment, such as TV receiver or a video tape recorder, by a personal computer. However, it becomes necessary in this case to add an interfacing circuit in order to effect a commander function not present in the personal computer, with consequent rise in costs. Besides, such addition of the interfacing circuit to the portable personal computer leads to an increased size of the personal computer.